1. Field of the Invention
The present invention relates to orthopaedic instruments, and, more particularly, to orthopaedic implant impactors.
2. Description of the Related Art
The hip joint is configured as a ball and socket arrangement which includes the femoral head joined to the natural socket or acetabulum located in the pelvis. Deterioration of the acetabulum and/or femoral head can be brought about by injury or progressive diseases such as osteoarthritis. When injury or disease occurs, the damaged component(s) can be replaced or rebuilt using appropriate orthopaedic implants. In the technique known as a “total hip replacement”, one method involves cementing or press-fitting an acetabular cup prosthesis into the acetabulum after the acetabulum has been sufficiently reamed to accept the cup. Additionally, fixation fasteners can be used to hold the cup in the acetabulum, and the cup can include a porous coating on the convex side to promote bone ingrowth. The femoral head can also typically be replaced.
In order to properly seat an acetabular cup into the acetabulum an impaction tool, or impactor, is used by the surgeon to firmly seat the cup. The impactor needs to securely hold the cup while the cup is being located in the acetabulum, and the impactor also needs to securely hold the cup while the cup is being impacted into the acetabulum. The acetabular cup impactor can include a surgical implement coupler which can be secured to the acetabular cup. An elongated shaft is joined to the surgical implement coupler at one end, and includes a striker cap at the opposite end of the shaft. The cup is seated in the prepared acetabulum by positioning the cup in the prepared depression, and imparting a series of blows from a mallet against the striker cap. The force of the blows is transmitted through the shaft of the impactor, to seat the cup in the prepared opening in the acetabulum. After the cup is properly seated, the surgical implement coupler of the impactor is detached from the cup.
Particularly in a minimally invasive procedure, where a small incision is made to reduce the trauma to surrounding tissue, at least two problems occur in seating an acetabular cup. It is difficult to properly align the impactor because of anatomical features that are in the way, and disconnecting the head from the cup is more difficult with limited access to the end of the tool. Cleaning and sterilization of the impactor after surgery can also be difficult.
An acetabular cup impactor is known with a curved shaft that makes proper alignment of the tool more easily accomplished during a minimally invasive surgical procedure, and includes a remotely activated surgical implement coupler for disengaging the head from an acetabular cup. The surgical implement coupler is adapted for selective attachment to and detachment from an orthopedic device such as an acetabular cup. The surgical implement coupler includes a threaded stud rotatably disposed in and retained by a sleeve. The threaded stud is adapted for threaded engagement with an acetabular cup or other orthopedic device. A universal joint or swivel drive is disposed rotatably in the shaft assembly and is drivingly connected to the threaded stud such that rotation of the swivel drive causes rotation of the threaded stud in the sleeve. A thumb wheel near the handle of the impactor actuates the swivel drive. A problem with this design is that it requires the threaded stud to be threaded into the acetabular cup, and this threading process can be tedious and time consuming, and can result in crossthreading the threaded stud into the acetabular cup with a resultant less than secure connection between the threaded stud and the acetabular cup. Another problem with this design is that it is substantially closed along the shaft which makes the internal components, such as the swivel drive, difficult to clean and sterilize.
An acetabular cup impactor or inserter is known with a curved shaft and which encloses a drive train and which includes at a far end, a prosthesis (acetabular cup, for example) engaging collet, and at the opposite end, a knob or handle which facilitates turning of the drive train by the operator. When knob is turned in one direction, the prosthesis-engaging collet locks the prosthesis against rotational movement. Further, the collet action eliminates the need of threading the acetabular prosthesis on the end of the inserter as the prosthesis can simply be placed over the collet and the collet expanded so as to grip the internal threads of the prosthesis. Turning the knob in the opposite direction can release the collet from the prosthesis. Although this design eliminates the need to thread the collet into the cup, the knob is relatively far from the impactor handle, and because of the rotational movement required by the knob, releasing the cup from the impactor is a two handed operation. Further, it is largely a closed design which makes the drive train difficult to clean and sterilize.
What is needed in the art is an orthopaedic implant impactor which is easy to use in a minimally invasive procedure, which can engage and release a prosthesis with a simple motion and which is easy to clean.